Mixture control system



Nov. 27, 1945. c. 1. MacN ElL EI'AL MIXTURE CONTROL SYSTEM Filed Sept. 5, 1942 52: SEE @332 TORS Motif [Mar flail W INVEN flank at Charles EN &

M mmt kwbwrfi Patented Nov. 27, 1945 MIXTURE CONTROL SYSTEM Charles I. MaeNeil, Glen Ridge, N. J., and Frank C. Mock, South poration of Delaware Bend, Ind., assignors to Bendix Aviation Corporation South Bend, Ind., a cor- Application September 5, 1942, Serial No. 457,506

4 Claims.

This invention relates to mixture control systems, and more particularly, to a system for automatically regulating the fuel mixture of an internal combustion engine.

It is recognized that the efficiency of an internal combustion engine can be affected by the quality of the air and gasoline mixture supplied to the intake of the engine. It is well understood that the quality of the intake fuel mixture is refiected in the composition of gases in the exhaust of the engine. Therefore, systems have been devised in the past to indicate the optimum fuel mixture in accordance with a determined standard of exhaust gas composition, and variations from this standard are indicated so that the air intake or gasoline intake can be throttled to restore the fuel and air mixture to the ratio proper for economic use of the engine. One well recognized system for indicating exhaust ga quality is set forth in the patent to Heinicke, No. 1,646,247.

Several systems for regulating the fuel-to-air ratio, in accordance with input pressure and temperature conditions, have been devised, and one of these systems is shown in the patent to Hiscock, No. 2,082,397.

It is an object of the vide a fuel mixture control system wherein the fuel-to-air ratio is maintained in accordance with a predetermined quality of the exhaust gases.

It is another object of the invention to provide a, system including a motor drive for regulating the fuel mixture of the input of an internal combustion engine, to maintain the mixture at a standard determined by a particular composition of engine exhaust gases.

Other objects of the invention include the provision of a system wherein variations of exhaust gas quality from a determined standard are represented as electrical currents for automatically controlling the mixture of fuel and air supplied to an engine, and the provision of a system wherein the fuel and air mixture is automatically maintained through a motor control free of'excessive hunting in the regulating system.

Other objects of the invention will appear from a study of the following specification when made in conjunction with the attached drawings, throughout which like numerals designate like parts, and wherein the sole figure is a schematic diagram of one embodiment of a fuel mixture control system of the present invention.

In accordance with the present invention, motor control means connected to a mixture control unit is regulated by electrical currents representing variation from standard exhaust gas present invention to procomposition, through the medium of a vacuum tube amplifier having a marginal relay unit in its output for selectively operating the motor control. Hunting of the motor control and overcontrol are prevented by the use of a switching device periodically rendering the motor control inoperative for definite portions of time, during which, the exhaust gas analyzer will be prevented from changing the fuel mixture through the motor control system.

Having reference to the drawing, 10 represents an exhaust gas analyzer of the type described in the above-identified Heinicke patent, with a Wheatstone bridge having one branch I l enclosed in a standard gas chamber within casing l2, and another arm l3 enclosed in a chamber within housing l2 that is open to gases from engine exhaust pipe 14, through conduits l5 and I6. Two other arms of the Wheatstone bridge are represented by equal resistors I! and I8, joined together at point I 9, and connected through lead 20 to the battery 2|. The arms H and I3 are connected together at point 22 and to battery 2| through conductor 23, ammeter 24 and a variable resistance 25. The path between points is and 22 forms one diagonal of a standard Wheatstone bridge.

As so far described, device I0 is similar to the exhaust gas analyzer set forth in the Heinicke patent; however, in place of the diagonal containing galvanometer 20 in the Heinicke patent, there is substituted a resistance 26 connected into the bridge at point 21 between arms H and I1 endpoint 28 between arms l3 and I8.

It is believed unnecessary to describe the manner in which the bridge is unbalanced by virtue of variations of exhaust gas from a determined standard of composition, since'the Heinlcke patent gives a full explanation thereof. It is intended that the bridge be balanced when the exhaust gas composition is standard. Therefore, when the exhaust gas composition surrounding arm i3 is the same as the standard gas composition surrounding arm I I the current in resistor 26 is zero.

Resistor 26 is connected through a conductor 29 to the control grid 30 of a conventional triode 3|, and to ground through conductor 32. Grid 30 has its bias adjusted by variable resistance 33 to a particular value to fulfill a condition of current flow that will be described later. Anode 34 is connected through conductor 35 to the control grid 36 of a second triode 31. A battery 38 or other suitable source of anode potential is connected in the conventional manner to anode 34 through conductor 40, resistor 4| and conductor 35. Anode 42 of triode 31 is connected to battery 38 by means of conductor 43. In series with anode 42 in the battery circuit including battery 38 and conductor 43, there is connected a solenoid 44 of a relay 45 having an armature 46, a magnetic core 41, a front contact 48 and a back contact 49. Armature 46 is biased to close against back contact 49 by virtue of a spring member 50. Armature 46 carries a contact at its outer end and is connected in circuit with a switch 53 by means of conductor 54, and with either of the oppositely poled field windings 55 and 56 through the contacts 49 and 48, respectively. Field windings 55 and 56 are part of a shunt-wound motor 51 having an armature 58. Motor 51 is in circuit with battery 59 through conductors 54, 60, 6| and 62, and the application of electrical energy to motor 51 is controlled by a master circuit switch 53 and a thermostatically responsive switch 63 having contacts 64 and 65.

A fuel mixture control unit, which may be of the type shown in the Hiscock patent, is shown at 66. schematically, the mixture varying mechanism of unit 66 may be represented as a valve 61 having connection through any suitable linkage 68, with shaft 69 of motor 51.

Marginal relay 45 is so adjusted that for a determined value of current flow through solenoid 44, armature 46 will be held by magnetic attraction in its neutral or open position, as shown, against the pull of spring 50. The proper current through solenoid 44 to obtain this condition is fixed by the value of biasing voltage of grid 30 obtained through self-biasing resistor 33. With zero signal current, that is, with no flow through resistor 26 (which is the condition for a balanced bridge Hi), the bias on grid 30 is set so that the grid draws just enough current that, when amplified in triode 31, will bring about current in the circuit of anode 42 sufficient to pull armature 46 into the neutral position shown.

When bridge Ill becomes unbalanced in one direction, for example, in response to an analysis of too lean a mixture, current will flow through resistor 26 in one direction. When bridge Ill becomes unbalanced in the other direction, in response to an analysis of too rich a mixture, current will flow through resistor 26 in the opposite direction. For one of these unbalanced conditions, grid 30 will thus become more negative, resulting in a decreased current through solenoid 44, permitting contact 5| to be pulled against back contact 49. For the other of these unbalanced conditions, grid 36 will become more positive, resulting in an increase of current through solenoid 44 beyond the value necessary to hold armature 46 in the neutral position. Thus, contact 5| will be closed against front contact 48.

Switch 53 is closed by the pilot or operator having control of the engine under consideration. Thermostatic switch 63 is closed in its cold condition, and when heated to a determined value, it is opened by the unequal expansion of two metals of a conventional bimetallic unit. Assuming that the bridge is balanced, that is, conr tact 5| is in its neutral position, and switches 63 and 53 are closed, no adjustment will be made of the mixture control unit, since neither of the oppositely poled fields 55 or 56 is energized.

Assuming that the exhaust analyzing bridge l0 has become unbalanced because of the combustion of a leaning mixture, then current may flow in one direction, for example, downwardly, through resistor 26, making grid 30 less positive,

and the amplified current in circuit with anode 42 and passing through solenoid 44 therefore falls, permitting contact 5| to close against back contact 49. This places field 55 in circuit with the motor, and rotation of shaft 69 will be in a direction suitable to enrich the fuel mixture. Rotation of shaft 69 may be restricted to a few seconds by the thermostatic setting of switch 63, which may be designed to open when the heat generated by the current-due to a few seconds operation of the motor causes the required expansion of the dissimilar metals to open contacts 64 and 65. Meanwhile, the gases analyzed for the new mixture may indicate that the mixture is correct. The bridge will be then balanced, and thus, the current in resistor 26 drops to zero, restoring the normal current through solenoid 44, causing armature 46 to be pulled into the neutral position shown. During this interval, switch 63 closes due to cooling of the thermostatic element.

Assuming that the bridge now becomes unbalanced because of a gas composition indicating a too rich'mixture, current will flow through resistor 26 in the opposite direction, for example, upwardly, causing grid 30 to become more positive, thus drawing more current and resulting in an increased current through solenoid 44, which draws armature 46 downwardly, so that contact 5| closes against front contact 46, placing field 56 in circuit, causing shaft 69 to rotate in the 0pposite direction and operate valve 61 of the mixture control unit to lean the mixture for a definite period of two or three seconds, at the end of which time thermostatic switch 63 is again opened by the heat of the current carried in the circuit of motor 51.

It will be seen that complete motor control of the fuel mixture may be provided so that once a standard fuel-to-air ratio is fixed for the optimum operation of the engine, variations therefrom may be corrected. The thermostatic switch 63 limits the operation of the motor 51 to a few seconds for any particular adjustment, and therefore, the liability to hunting is minimized.

The amplifying system shown is intended to be conventional. The use of an amplifier of other well known design, is, of course, intended to be within the scope of the invention. Also, the intermittently operating switch 63 need not be thermostatically controlled, but might be motor controlled by a small auxiliary motor. It is believed that other changes within the scope of the invention will be apparent to one skilled in the art. It is therefore intended not to limit the invention to the embodiment chosen as an example of the invention, but solely by the scope of the appended claims.

What is claimed is:

1. An automatic mixture control system comprising an exhaust gas analyzer circuit of the type in which variations from a known exhaust gas composition result in the flow of an electrical current of value varying in accordance with the departure of the exhaust gas composition from a determined standard, a reversible motor, a circuit for energizing said motor, a mixture control shaft rotatable by said motor, means included in said analyzer circuit for causing said motor to operate directionally to change the fuel mixture in response to deviation from the determined standard condition, and thus restore the exhaust gas composition to the determined standard, a temperature-controlled means in the motor circuit, and a heater electrically energized by the motor circuit so as to cause said temperature-controlled means to periodically interrupt said circuit independently of the gas composition condition then prevailing.

2. An automatic fuel mixture control system comprising an exhaust gas analyzer. an amplifier, a first reversible motor and a mixture control unit, said unit having a rotatable shaft through which fuel mixture may be varied, said exhaust gas analyzer including an electrical element through which currents fiow when the exhaust gas varies in analysis from a determined standard, said electrical element being connected to the input of said amplifier. control means in the output of said amplifier for governing the operation and the direction of operation of said first reversible motor, connections between said shaft and said motor, a second motor means for controlling the energizing circuit of said first reversible motor, a winding for energizing said second motor means, said Winding connected in series with said control means to periodically energize the second motor means so as to interrupt the operation of said first motor during rotation of said shaft in response to current flowing through said electrical element in accordance with variations of said gas analysis from the determined standard.

3. An automatic mixture control system comprising an exhaust gas analyzer circuit of the type in which variations from a known exhaust gas composition result in the flow of an electrical current of value varying in accordance with the departure of the exhaust gas composition from a determined standard, a reversible motor, a circuit for energizing said motor, a mixture control shaft rotatable by said motor, means included in said analyzer circuit for controlling the energization of said motor circuit so as to cause said motor to operate directionally to change the fuel mixture in response to deviation from the determined standard condition, and thus restore the exhaust gas composition to the determined standard, and means responsiveto the energization of the motor circuit to periodically interrupt said motor circuit independently of the gas composition condition then prevailing.

4. An automatic mixture control system comprising an exhaust gas analyzer circuit of the type in which variations from a known exhaust gas composition result in the flow of an electrical current of a value varying in accordance with the departure of the exhaust gas composition from a determined standard, a reversible motor, a mixture control shaft rotatable by said motor, an electronic amplifier, said exhaust gas analyzer circuit being connected to the input of said electronic amplifier, an electromagnet connected in the output of said amplifier, a spring biased switch arm means actuated by said electromagnet to control the energization of the motor circuit and to cause the motor to operate directionally to change the fuel mixture in response to deviations from the determined standard condition and thus restore the exhaust gas composition to the determined standard, a temperature responsive element and a heater element, both of said elements connected in series with said switch arm means and said motor means to periodically interrupt the motor circuit during the energization of said circuit,

CHARLES I. MACNEIL. FRANK C. MOCK. 

